Comfort, comfort my people, says your God.
 Speak tenderly to Jerusalem,
and cry to her that her warfare is ended, that her iniquity is pardoned, that she has received from the LORD's hand double for all her sins.  A voice cries: “In the wilderness prepare the way of the LORD; make straight in the desert a highway for our God.  Every valley shall be lifted up, and every mountain and hill be made low; the uneven ground shall become level, and the rough places a plain.  And the glory of the LORD shall be revealed, and all flesh shall see it together, for the mouth of the LORD has spoken.”
At this point, Isaiah is comforting people after 39 chapters of prophesy about the coming destruction. The interesting part here is how this gets interpreted in the New Testament.
The scene is one of doom and destruction. Foreign armies are coming and everything the Jewish people know and love is going to be laid to waste. They’ve been serving golden idols, trusting in witches and fortune-tellers, and making allies with foreign countries that God told them to stay away from. They haven’t been trusting in or calling on the Name of the Lord for any of their help.
A lost people without a Shepherd to guide or care for them are crying out for help. The help comes in the wilderness. Every mountain (obstacle, exalted and lofty thing) is being wiped out and leveled. The path to and from God is about to be made smooth.
That same phrase is how John the Baptist explains himself. He is the one doing this task that is called for in Isaiah 40. That means that what comes next is “the glory of the LORD shall be revealed.”
What came next after John the Baptist? JESUS! The Glory of God was revealed in Jesus Christ when He came and lived a life like ours. When He came to live a perfect life and turn people back to God, the full glory of God was on display. When He died on the cross and rose from the dead, that was the Glory of God in action.
It had appeared like a fire, like a pillar of smoke, like angels and deliverance, but ultimately the Glory of God is Jesus.
All flesh, all creation, was in a position to see the Glory of God as Christ walked around the Middle East 2000 years ago. Now, as we are left with the Holy Spirit, the scriptures, and our Church body, we can look for the Glory of God in Christ too.
As we pray and seek Him, we’ll see Him more and more. That is God’s desire for us all.